package com.xywy.lucene.util;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.MultiReader;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.FSDirectory;

import java.io.File;
import java.io.IOException;
import java.nio.file.Paths;
import java.util.Set;
import java.util.concurrent.ExecutorService;

/**lucene索引查询工具类
 * @author lenovo
 *
 */
public class SearchUtil {
    /**获取IndexSearcher对象
     * @param service
     * @return
     * @throws IOException
     */
    public static IndexSearcher getIndexSearcherByParentPath(String parentPath,ExecutorService service) {
        MultiReader reader = null;
        //设置
        try {
            File[] files = new File(parentPath).listFiles();
            IndexReader[] readers = new IndexReader[files.length];
            for (int i = 0 ; i < files.length ; i ++) {
                readers[i] = DirectoryReader.open(FSDirectory.open(Paths.get(files[i].getPath(), new String[0])));
            }
            reader = new MultiReader(readers);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new IndexSearcher(reader,service);
    }
    /**根据索引路径获取IndexReader
     * @param indexPath
     * @return
     * @throws IOException
     */
    public static DirectoryReader getIndexReader(String indexPath) throws IOException{
        return DirectoryReader.open(FSDirectory.open(Paths.get(indexPath, new String[0])));
    }
    /**根据索引路径获取IndexSearcher
     * @param indexPath
     * @param service
     * @return
     * @throws IOException
     */
    public static IndexSearcher getIndexSearcherByIndexPath(String indexPath,ExecutorService service) throws IOException{
        IndexReader reader = getIndexReader(indexPath);
        return new IndexSearcher(reader,service);
    }

    /**如果索引目录会有变更用此方法获取新的IndexSearcher这种方式会占用较少的资源
     * @param oldSearcher
     * @param service
     * @return
     * @throws IOException
     */
    public static IndexSearcher getIndexSearcherOpenIfChanged(IndexSearcher oldSearcher,ExecutorService service) throws IOException{
        DirectoryReader reader = (DirectoryReader) oldSearcher.getIndexReader();
        DirectoryReader newReader = DirectoryReader.openIfChanged(reader);
        return new IndexSearcher(newReader, service);
    }



    /**根据IndexSearcher和docID获取默认的document
     * @param searcher
     * @param docID
     * @return
     * @throws IOException
     */
    public static Document getDefaultFullDocument(IndexSearcher searcher,int docID) throws IOException{
        return searcher.doc(docID);
    }
    /**根据IndexSearcher和docID
     * @param searcher
     * @param docID
     * @param listField
     * @return
     * @throws IOException
     */
    public static Document getDocumentByListField(IndexSearcher searcher,int docID,Set<String> listField) throws IOException{
        return searcher.doc(docID, listField);
    }

    /**分页查询
     * @param page 当前页数
     * @param perPage 每页显示条数
     * @param searcher searcher查询器
     * @param query 查询条件
     * @return
     * @throws IOException
     */
    public static TopDocs getScoreDocsByPerPage(int page,int perPage,IndexSearcher searcher,Query query) throws IOException{
        TopDocs result = null;
        if(query == null){
            System.out.println(" Query is null return null ");
            return null;
        }
        ScoreDoc before = null;
        if(page != 1){
            TopDocs docsBefore = searcher.search(query, (page-1)*perPage);
            ScoreDoc[] scoreDocs = docsBefore.scoreDocs;
            if(scoreDocs.length > 0){
                before = scoreDocs[scoreDocs.length - 1];
            }
        }
        result = searcher.searchAfter(before, query, perPage);
        return result;
    }
    public static TopDocs getScoreDocs(IndexSearcher searcher,Query query) throws IOException{
        TopDocs docs = searcher.search(query, getMaxDocId(searcher));
        return docs;
    }
    /**统计document的数量,此方法等同于matchAllDocsQuery查询
     * @param searcher
     * @return
     */
    public static int getMaxDocId(IndexSearcher searcher){
        return searcher.getIndexReader().maxDoc();
    }

}